Boot Order Change

Installs of both stretch and buster modify the boot order such that
"debian" is first under "UEFI Boot Sources". After installation, the
bios menu has to be edited in order to boot from DVD or CD or USB
drive. Also "Hard Drive" has been replaced with "debian".
The PC is:
Hewlett-Packard HP Pro 3400 Series MT/2ABF, BIOS 7.16 03/23/2012
Apparently it is deliberate, so what is the reason for this?
- Dan